Generalized coupled-mode theory for X(2) interactions in finite multilayered structures

Using a first-order multiple-scale expansion approach, we derive a set of coupled-mode equations that describe both forward and backward second-harmonic generation and amplification processes in nonlinear, one-dimensional, multilayered structures of finite length. The theory is valid for index modulation of arbitrary depth and profile. We derive analytical solutions in the undepleted pump regime under different pumping circumstances. The model shows excellent agreement with the numerical integration of Maxwell's equations. (C) 2002 Optical Society of America.